Methods and system for adjusting level of tactile content when presenting audio content

ABSTRACT

An audio system presented herein includes a transducer array, a sensor array, and a controller. The transducer array presents audio content to a user. The controller controls the transducer array to adjust a level of tactile content imparted to the user via actuation of at least one transducer in the transducer array while presenting the audio content to the user. The audio system can be part of a headset.

FIELD OF THE INVENTION

This disclosure relates generally to artificial reality systems, andmore specifically to an audio system configured to adjust a level oftactile content when presenting audio content in artificial realitysystems.

BACKGROUND

Head-mounted displays in artificial reality systems often includefeatures such as speakers or personal audio devices to provide audiocontent to users of the head-mounted displays. In some instances,conventional head-mounted display may use bone conduction and/orcartilage conduction to provide audio content to the user. However, atcertain frequencies and amplitudes in addition to hearing the audiocontent, the audio content may be perceived by the user (e.g., viamechanoreceptors embedded in tissues) as tactile stimulation.

SUMMARY

Embodiments of the present disclosure support an audio system, a method,and a computer readable medium for providing content to a user, e.g.,wearer of a headset. The audio system includes a transducer arrayconfigured to present the content to the user. The audio system furtherincludes a controller configured to control the transducer array toadjust a level of tactile content imparted to the user via actuation ofat least one transducer in the transducer array while presenting audiocontent to the user. The audio system can be integrated as part of theheadset.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of a headset implemented as an eyeweardevice, in accordance with one or more embodiments.

FIG. 1B is a perspective view of a headset implemented as a head-mounteddisplay, in accordance with one or more embodiments.

FIG. 2A is a block diagram of an audio system, in accordance with one ormore embodiments.

FIG. 2B is an example graph illustrating a tactility threshold level foractuation of a transducer in the audio system of FIG. 2A as a functionof frequency, in accordance with one or more embodiments.

FIG. 3 is a flowchart illustrating a process for adjusting a level oftactile content while presenting audio content, in accordance with oneor more embodiments.

FIG. 4 is a flowchart illustrating a process for controlling tactilecontent presented to a user, in accordance with one or more embodiments.

FIG. 5 is a system that includes a headset, in accordance with one ormore embodiments.

The figures depict various embodiments for purposes of illustrationonly. One skilled in the art will readily recognize from the followingdiscussion that alternative embodiments of the structures and methodsillustrated herein may be employed without departing from the principlesdescribed herein.

DETAILED DESCRIPTION

A transducer placed in a proximity of an outer ear can create (e.g., byexciting a certain tissue) acoustic pressure waves inside an ear-canalthat can be perceived by a person as sound. At certain frequencies whenexcitation levels increase, the person (e.g., via mechanoreceptorsembedded in tissues) may start sensing tactile sensations (i.e., senseof touch). Embodiments of the present disclosure relate to an audiosystem that controls and adjust a level of tactile content presented toa user of the audio system.

An audio system for controlling a modality (i.e., audio only, tactileonly or combination of audio/tactile) of presented content is enclosedherein. The audio system includes a transducer array, a sensor array,and an audio controller. The transducer array presents content to a uservia, e.g., cartilage conduction, bone conduction, air conduction, orsome combination thereof. The sensor array detects sounds produced bythe transducer array. The sensor array may include at least one acousticsensor and/or at least one vibration sensor (i.e., an accelerometer).The audio controller may control, based on the detected sounds, thetransducer array to adjust a level of tactile feedback that may beimparted to the user via actuation of one or more transducers in thetransducer array while presenting content. In some embodiments, theaudio controller adjusts the level of tactile feedback such that theuser does not perceive any tactile content. The audio controller mayadjust the level of tactile feedback using, e.g., a perception model,which may be specific to the user and obtained via a calibrationprocess. In some embodiments, the audio controller controls thetransducer array to control tactile content that is imparted to the uservia actuation of one or more transducers in the transducer array. In oneor more embodiments, at least one transducer in the transducer array isconfigured to induce tissue vibrations (e.g., skin vibrations) strongenough to be felt as tactile sensation (e.g., touch). The tactilecontent that is intentionally controlled to be perceived by the user maybe utilized for, e.g., providing navigation instructions to the user,increasing speech intelligibility, providing near field effect, somecombination thereof, etc.

The audio system presented herein may be part of a headset. The headsetmay be, e.g., a near eye display (NED), a head-mounted display (HMD), orsome other type of headset. The headset may be part of an artificialreality system. The headset further includes a display and an opticalassembly. The display of the headset is configured to emit image light.The optical assembly of the headset is configured to direct the imagelight to an eye box of the headset corresponding to a location of auser's eye. In some embodiments, the image light may include depthinformation for a local area surrounding the headset. Alternatively oradditionally, the audio system presented herein may operate inconjunction with a set of smart headphones having cartilage conductionactuator(s) and/or bone conduction actuator(s).

The audio system presented herein controls and adjusts a level oftactile content presented to a user of the audio system. The tactilecontent could be often considered a nuisance. The audio system presentedherein is configured to turn the tactile content into information usefulfor the user. The audio system presented herein can also be configuredto mitigate the tactile content such that the tactile content is notperceived by the user.

Embodiments of the invention may include or be implemented inconjunction with an artificial reality system. Artificial reality is aform of reality that has been adjusted in some manner beforepresentation to a user, which may include, e.g., a virtual reality (VR),an augmented reality (AR), a mixed reality (MR), a hybrid reality, orsome combination and/or derivatives thereof. Artificial reality contentmay include completely generated content or generated content combinedwith captured (e.g., real-world) content. The artificial reality contentmay include video, audio, haptic feedback, or some combination thereof,any of which may be presented in a single channel or in multiplechannels (such as stereo video that produces a three-dimensional effectto the viewer). Additionally, in some embodiments, artificial realitymay also be associated with applications, products, accessories,services, or some combination thereof, that are used to create contentin an artificial reality and/or are otherwise used in an artificialreality. The artificial reality system that provides the artificialreality content may be implemented on various platforms, including awearable device (e.g., headset) connected to a host computer system, astandalone wearable device (e.g., headset), a mobile device or computingsystem, or any other hardware platform capable of providing artificialreality content to one or more viewers.

FIG. 1A is a perspective view of a headset 100 implemented as an eyeweardevice, in accordance with one or more embodiments. In some embodiments,the eyewear device is a NED. In general, the headset 100 may be worn onthe face of a user such that content (e.g., media content) is presentedusing a display assembly and/or an audio system. However, the headset100 may also be used such that media content is presented to a user in adifferent manner. Examples of media content presented by the headset 100include one or more images, video, audio, or some combination thereof.The headset 100 includes a frame, and may include, among othercomponents, a display assembly including one or more display elements120, a depth camera assembly (DCA), an audio system, and a positionsensor 190. While FIG. 1A illustrates the components of the headset 100in example locations on the headset 100, the components may be locatedelsewhere on the headset 100, on a peripheral device paired with theheadset 100, or some combination thereof. Similarly, there may be moreor fewer components on the headset 100 than what is shown in FIG. 1A.

The frame 110 holds the other components of the headset 100. The frame110 includes a front part that holds the one or more display elements120 and end pieces (e.g., temples) to attach to a head of the user. Thefront part of the frame 110 bridges the top of a nose of the user. Thelength of the end pieces may be adjustable (e.g., adjustable templelength) to fit different users. The end pieces may also include aportion that curls behind the ear of the user (e.g., temple tip, earpiece).

The one or more display elements 120 provide light to a user wearing theheadset 100. As illustrated in FIG. 1A, the headset 100 includes adisplay element 120 for each eye of a user. In some embodiments, adisplay element 120 generates image light that is provided to an eyeboxof the headset 100. The eyebox is a location in space that an eye ofuser occupies while wearing the headset 100. For example, a displayelement 120 may be a waveguide display. A waveguide display includes alight source (e.g., a two-dimensional source, one or more line sources,one or more point sources, etc.) and one or more waveguides. Light fromthe light source is in-coupled into the one or more waveguides whichoutputs the light in a manner such that there is pupil replication in aneyebox of the headset 100. In-coupling and/or outcoupling of light fromthe one or more waveguides may be done using one or more diffractiongratings. In some embodiments, the waveguide display includes a scanningelement (e.g., waveguide, mirror, etc.) that scans light from the lightsource as it is in-coupled into the one or more waveguides. Note that insome embodiments, one or both of the display elements 120 are opaque anddo not transmit light from a local area around the headset 100. Thelocal area is the area surrounding the headset 100. For example, thelocal area may be a room that a user wearing the headset 100 is inside,or the user wearing the headset 100 may be outside and the local area isan outside area. In this context, the headset 100 generates VR content.Alternatively, in some embodiments, one or both of the display elements120 are at least partially transparent, such that light from the localarea may be combined with light from the one or more display elements toproduce AR and/or MR content.

In some embodiments, a display element 120 does not generate imagelight, and instead is a lens that transmits light from the local area tothe eyebox. For example, one or both of the display elements 120 may bea lens without correction (non-prescription) or a prescription lens(e.g., single vision, bifocal and trifocal, or progressive) to helpcorrect for defects in a user's eyesight. In some embodiments, thedisplay element 120 may be polarized and/or tinted to protect the user'seyes from the sun.

Note that in some embodiments, the display element 120 may include anadditional optics block (not shown). The optics block may include one ormore optical elements (e.g., lens, Fresnel lens, etc.) that direct lightfrom the display element 120 to the eyebox. The optics block may, e.g.,correct for aberrations in some or all of the image content, magnifysome or all of the image, or some combination thereof.

The DCA determines depth information for a portion of a local areasurrounding the headset 100. The DCA includes one or more imagingdevices 130 and a DCA controller (not shown in FIG. 1A), and may alsoinclude an illuminator 140. In some embodiments, the illuminator 140illuminates a portion of the local area with light. The light may be,e.g., structured light (e.g., dot pattern, bars, etc.) in the infrared(IR), IR flash for time-of-flight, etc. In some embodiments, the one ormore imaging devices 130 capture images of the portion of the local areathat include the light from the illuminator 140. As illustrated, FIG. 1Ashows a single illuminator 140 and two imaging devices 130. In alternateembodiments, there is no illuminator 140 and at least two imagingdevices 130.

The DCA controller computes depth information for the portion of thelocal area using the captured images and one or more depth determinationtechniques. The depth determination technique may be, e.g., directtime-of-flight (ToF) depth sensing, indirect ToF depth sensing,structured light, passive stereo analysis, active stereo analysis (usestexture added to the scene by light from the illuminator 140), someother technique to determine depth of a scene, or some combinationthereof.

The audio system provides audio content. The audio system includes atransducer array, a sensor array, and an audio controller 150. However,in other embodiments, the audio system may include different and/oradditional components. Similarly, in some cases, functionality describedwith reference to the components of the audio system can be distributedamong the components in a different manner than is described here. Forexample, some or all of the functions of the audio controller 150 may beperformed by a remote server.

The transducer array presents sound to user. The transducer arrayincludes a plurality of transducers. A transducer may be a speaker 160or a tissue transducer 170 (e.g., a bone conduction transducer or acartilage conduction transducer). As shown in FIG. 1A, the speakers 160may be enclosed in the frame 110. In some embodiments, instead ofindividual speakers for each ear, the headset 100 includes a speakerarray comprising multiple speakers integrated into the frame 110 toimprove directionality of presented audio content, e.g., usingbeamforming array processing. The tissue transducer 170 couples to thehead of the user and directly vibrates tissue (e.g., bone or cartilage)of the user to generate sound. The number and/or locations oftransducers may be different from what is shown in FIG. 1A.

The sensor array detects sounds within the local area of the headset100. In some embodiments, the sensor array includes a plurality ofacoustic sensors 180. An acoustic sensor 180 captures sounds emittedfrom one or more sound sources in the local area (e.g., a room). Eachacoustic sensor is configured to detect sound and convert the detectedsound into an electronic format (analog or digital). The acousticsensors 180 may be acoustic wave sensors, microphones, soundtransducers, or similar sensors that are suitable for detecting sounds.

In some embodiments, one or more acoustic sensors 180 may be placed inan ear canal of each ear (e.g., acting as binaural microphones). In someembodiments, the acoustic sensors 180 may be placed on an exteriorsurface of the headset 100, placed on an interior surface of the headset100, separate from the headset 100 (e.g., part of some other device), orsome combination thereof. The number and/or locations of acousticsensors 180 may be different from what is shown in FIG. 1A. For example,the number of acoustic detection locations may be increased to increasethe amount of audio information collected and the sensitivity and/oraccuracy of the information. The acoustic detection locations may beoriented such that the microphone is able to detect sounds in a widerange of directions surrounding the user wearing the headset 100.

In some other embodiments, the sensor array includes a plurality ofvibration sensors, e.g., accelerometers. The accelerometers captureinformation about acceleration of vibration which is used to controland/or adjust amplitude levels of sound signals. The accelerometer maybe embedded into the frame 110. Alternatively, the accelerometer may bepositioned to be in contact with a tissue at a proximity of atransducer, e.g., the tissue transducer 170. Additionally, a proximitysensor can also be used to ensure that the tissue transducer 170 (e.g.,the cartilage conduction transducer) is in a proper location.

The audio controller 150 processes information from the sensor arraythat describes sounds detected by the sensor array. The audio controller150 may comprise a processor and a computer-readable storage medium. Theaudio controller 150 may be configured to generate direction of arrival(DOA) estimates, generate acoustic transfer functions (e.g., arraytransfer functions and/or head-related transfer functions), track thelocation of sound sources, form beams in the direction of sound sources,classify sound sources, generate sound filters for the speakers 160, orsome combination thereof.

In some embodiments, the audio controller 150 controls the transducerarray to adjust a level of tactile content imparted to the user wearingthe headset 100 via actuation of at least one of the transducers (e.g.,the tissue transducer 170), e.g., while presenting audio content to theuser. The tactile content is generally a byproduct of the audio content,and the same transducer(s) producing the audio can also produce thetactile content. The audio controller 150 may be configured to generatecontent of a different modality for presentation to the user. The audiocontroller 150 may be configured to generate the content that is audioonly, tactile only, or a combination of audio and tactile. Additionally,the audio controller 150 may be configured to mitigate both audiocontent and tactile content, such that no content is presented to theuser.

The audio controller 150 may adjust tactile content by adjusting one ormore actuation parameters of the at least one of the transducer. Anactuation parameter for a transducer may be a signal (e.g., mechanicalor electrical) that is used to actuate the transducer. An actuationparameter may be, e.g., a voltage, an electrical current, a mechanicalpressure, some other actuation signal, or some combination thereof. Theaudio controller 150 may adjust an actuation parameter of the at leastone transducer for a frequency band relative to a tactility thresholdlevel. Values of the actuation parameter below the threshold levelcorrespond to ranges of actuation where a portion of the tactile contentfor the frequency band is not perceived by the user, and values at orabove the threshold level correspond to ranges where the portion of thetactile content is perceived by the user. The acoustic sensors 180 maydetect sounds produced by the transducer array, e.g., the tissuetransducer 170 and/or the speaker 160. The audio controller 150 mayderive a tactility threshold level for the actuation parameter of thetissue transducer 170 for a frequency band, based on a portion of thedetected sounds within the frequency band. The audio controller 150 maythen adjust the actuation parameter to be below the tactility thresholdlevel when actuating the tissue transducer 170 for presentation of aportion of the tactile content within the frequency band.

In some embodiments, the audio controller 150 controls tactile contentimparted to the user wearing the headset 100 via actuation of at leastone of the transducers (e.g., the tissue transducer 170) whilepresenting audio content to the user so that the controlled tactilecontent is perceived by the user at certain times. In such cases, thetransducer array presents the audio content and the controlled tactilecontent to the user. In one or more embodiment, the audio controller 150uses the controlled tactile content to provide navigation instructionsto the user. For example, the audio controller 150 applies the tactilecontent to a corresponding tissue transducer 170 (e.g., a cartilageconduction transducer) attached to a corresponding ear of the user toprovide the navigation instructions to the user. In another embodiment,the audio controller 150 controls the tactile content to increase speechintelligibility for the audio content presented to the user. In yetanother embodiment, the audio controller 150 controls the tactilecontent to generate the audio content with a defined level of near fieldeffect. Additional details about operations of the audio controller 150and other components of the audio system are provided below inconnection with FIG. 2A, FIG. 3 and FIG. 4.

The position sensor 190 generates one or more measurement signals inresponse to motion of the headset 100. The position sensor 190 may belocated on a portion of the frame 110 of the headset 100. The positionsensor 190 may include an inertial measurement unit (IMU). Examples ofposition sensor 190 include: one or more accelerometers, one or moregyroscopes, one or more magnetometers, another suitable type of sensorthat detects motion, a type of sensor used for error correction of theIMU, or some combination thereof. The position sensor 190 may be locatedexternal to the IMU, internal to the IMU, or some combination thereof.

In some embodiments, the headset 100 may provide for simultaneouslocalization and mapping (SLAM) for a position of the headset 100 andupdating of a model of the local area. For example, the headset 100 mayinclude a passive camera assembly (PCA) that generates color image data.The PCA may include one or more RGB cameras that capture images of someor all of the local area. In some embodiments, some or all of theimaging devices 130 of the DCA may also function as the PCA. The imagescaptured by the PCA and the depth information determined by the DCA maybe used to determine parameters of the local area, generate a model ofthe local area, update a model of the local area, or some combinationthereof. Furthermore, the position sensor 190 tracks the position (e.g.,location and pose) of the headset 100 within the room. Additionaldetails regarding the components of the headset 100 are discussed belowin connection with FIG. 5.

FIG. 1B is a perspective view of a headset 105 implemented as a HMD, inaccordance with one or more embodiments. In embodiments that describe anAR system and/or a MR system, portions of a front side of the HMD are atleast partially transparent in the visible band (˜380 nm to 750 nm), andportions of the HMD that are between the front side of the HMD and aneye of the user are at least partially transparent (e.g., a partiallytransparent electronic display). The HMD includes a front rigid body 115and a band 175. The headset 105 includes many of the same componentsdescribed above with reference to FIG. 1A, but modified to integratewith the HMD form factor. For example, the HMD includes a displayassembly, a DCA, an audio system, and a position sensor 190. FIG. 1Bshows the illuminator 140, a plurality of the speakers 160, a pluralityof the imaging devices 130, a plurality of the acoustic sensors 180, andthe position sensor 190.

FIG. 2A is a block diagram of an audio system 200, in accordance withone or more embodiments. The audio system in FIG. 1A or FIG. 1B may bean embodiment of the audio system 200. The audio system 200 generatesone or more acoustic transfer functions for a user. The audio system 200may then use the one or more acoustic transfer functions to generateaudio content for the user. In the embodiment of FIG. 2A, the audiosystem 200 includes a transducer array 210, a sensor array 220, and anaudio controller 230. Some embodiments of the audio system 200 havedifferent components than those described here. Similarly, in somecases, functions can be distributed among the components in a differentmanner than is described here.

The transducer array 210 is configured to present content. The presentedcontent can be audio content, tactile content, or some combinationthereof. The transducer array 210 includes a plurality of transducers. Atransducer is a device that provides content, e.g., audio content,tactile content, or some combination thereof. A transducer may be, e.g.,a speaker (e.g., the speaker 160), a tissue transducer (e.g., the tissuetransducer 170), some other device that provides content, or somecombination thereof. A tissue transducer may be configured to functionas a bone conduction transducer or a cartilage conduction transducer.The transducer array 210 may present content via air conduction (e.g.,via one or more speakers), via bone conduction (via one or more boneconduction transducers), via cartilage conduction audio system (via oneor more cartilage conduction transducers), or some combination thereof.In some embodiments, the transducer array 210 may include one or moretransducers to cover different parts of a frequency range. For example,a piezoelectric transducer may be used to cover a first part of afrequency range and a moving coil transducer may be used to cover asecond part of a frequency range.

The bone conduction transducers generate acoustic pressure waves byvibrating bone/tissue in the user's head. A bone conduction transducermay be coupled to a portion of a headset, and may be configured to bebehind the auricle coupled to a portion of the user's skull. The boneconduction transducer receives vibration instructions from the audiocontroller 230, and vibrates a portion of the user's skull based on thereceived instructions. The vibrations from the bone conductiontransducer generate a tissue-borne acoustic pressure wave thatpropagates toward the user's cochlea, bypassing the eardrum.

The cartilage conduction transducers generate acoustic pressure waves byvibrating one or more portions of the auricular cartilage of the ears ofthe user. A cartilage conduction transducer may be coupled to a portionof a headset, and may be configured to be coupled to one or moreportions of the auricular cartilage of the ear. For example, thecartilage conduction transducer may couple to the back of an auricle ofthe ear of the user. The cartilage conduction transducer may be locatedanywhere along the auricular cartilage around the outer ear (e.g., thepinna, the tragus, some other portion of the auricular cartilage, orsome combination thereof). Vibrating the one or more portions ofauricular cartilage may generate: airborne acoustic pressure wavesoutside the ear canal; tissue born acoustic pressure waves that causesome portions of the ear canal to vibrate thereby generating an airborneacoustic pressure wave within the ear canal; or some combinationthereof. The generated airborne acoustic pressure waves propagate downthe ear canal toward the ear drum.

The transducer array 210 generates content in accordance withinstructions from the audio controller 230. In some embodiments, thecontent is spatialized. Spatialized content is content that appears tooriginate from a particular direction and/or target region (e.g., anobject in the local area and/or a virtual object). For example,spatialized content can make it appear that sound is originating from avirtual singer across a room from a user of the audio system 200. Thetransducer array 210 may be coupled to a wearable device (e.g., theheadset 100 or the headset 105). In alternate embodiments, thetransducer array 210 may be a plurality of speakers that are separatefrom the wearable device (e.g., coupled to an external console).

The sensor array 220 detects sounds within a local area surrounding thesensor array 220. The sensor array 220 may include a plurality ofacoustic sensors that each detect air pressure variations of a soundwave and convert the detected sounds into an electronic format (analogor digital). The plurality of acoustic sensors may be positioned on aheadset (e.g., headset 100 and/or the headset 105), on a user (e.g., inan ear canal of the user), on a neckband, or some combination thereof.An acoustic sensor may be, e.g., a microphone, a vibration sensor, anaccelerometer, or any combination thereof. In some embodiments, thesensor array 220 is configured to monitor the audio content generated bythe transducer array 210 using at least some of the plurality ofacoustic sensors. Increasing the number of sensors may improve theaccuracy of information (e.g., directionality) describing a sound fieldproduced by the transducer array 210 and/or sound from the local area.In some embodiments, at least one sensor of the sensor array 220 can beimplemented as a non-invasive electrode or an implant within a tissue ofthe user configured to sense firings of neurons when mechano-receptorsare active. Such implemented sensor(s) of the sensor array 220 candetect a tactile sensation of the user without any manual feedback fromthe user.

The audio controller 230 controls operation of the audio system 200. Inthe embodiment of FIG. 2A, the audio controller 230 includes a datastore 235, a DOA estimation module 240, a transfer function module 250,a tracking module 260, a beamforming module 270, a sound filter module280, and a tactility control module 285. The audio controller 230 may belocated inside a headset, in some embodiments. Some embodiments of theaudio controller 230 have different components than those describedhere. Similarly, functions can be distributed among the components indifferent manners than described here. For example, some functions ofthe controller may be performed external to the headset.

The data store 235 stores data for use by the audio system 200. Data inthe data store 235 may include sounds recorded in the local area of theaudio system 200, content (i.e., audio content, tactile content, orcombination thereof), head-related transfer functions (HRTFs), transferfunctions for one or more sensors, array transfer functions (ATFs) forone or more of the acoustic sensors, sound source locations, virtualmodel of local area, direction of arrival estimates, sound filters, oneor more perception models, actuation parameters, and other data relevantfor use by the audio system 200, or any combination thereof.

A perception model stored in the data store 235 may be used, e.g., bythe tactility control module 285, for adjusting a level of tactilecontent when presenting content to a user via the transducer array 210.A perception model may include information about a tactility thresholdlevel for at least one actuation parameter (e.g., an input voltage, aninput current, etc.) as a function of a frequency (or a frequency band)for actuating one or more transducers in the transducer array 210.Values of the actuation parameter below the threshold level for thefrequency band correspond to ranges of actuation where a portion of thetactile content for the frequency band is not perceived by the user, andvalues at or above the threshold level correspond to ranges where theportion of the tactile content is perceived by the user. Each perceptionmodel in the data store 235 may be unique for a specific user and/or aspecific acoustic environment (e.g., indoor environment, outdoorenvironment, an empty room, an occupied room, etc.). Alternatively, asingle perception model in the data store 235 may be common for multipleusers and/or multiple acoustic environments. In some embodiments, aperception model in the data store 235 may be obtained, e.g., by thetactility control module 285, by performing calibration of thetransducer array 210 for a specific user and/or a specific acousticenvironment where the audio system 200 is located.

The DOA estimation module 240 is configured to localize sound sources inthe local area based in part on information from the sensor array 220.Localization is a process of determining where sound sources are locatedrelative to the user of the audio system 200. The DOA estimation module240 performs a DOA analysis to localize one or more sound sources withinthe local area. The DOA analysis may include analyzing the intensity,spectra, and/or arrival time of each sound at the sensor array 220 todetermine the direction from which the sounds originated. In some cases,the DOA analysis may include any suitable algorithm for analyzing asurrounding acoustic environment in which the audio system 200 islocated.

For example, the DOA analysis may be designed to receive input signalsfrom the sensor array 220 and apply digital signal processing algorithmsto the input signals to estimate a direction of arrival. Thesealgorithms may include, for example, delay and sum algorithms where theinput signal is sampled, and the resulting weighted and delayed versionsof the sampled signal are averaged together to determine a DOA. A leastmean squared (LMS) algorithm may also be implemented to create anadaptive filter. This adaptive filter may then be used to identifydifferences in signal intensity, for example, or differences in time ofarrival. These differences may then be used to estimate the DOA. Inanother embodiment, the DOA may be determined by converting the inputsignals into the frequency domain and selecting specific bins within thetime-frequency (TF) domain to process. Each selected TF bin may beprocessed to determine whether that bin includes a portion of the audiospectrum with a direct path audio signal. Those bins having a portion ofthe direct-path signal may then be analyzed to identify the angle atwhich the sensor array 220 received the direct-path audio signal. Thedetermined angle may then be used to identify the DOA for the receivedinput signal. Other algorithms not listed above may also be used aloneor in combination with the above algorithms to determine DOA.

In some embodiments, the DOA estimation module 240 may also determinethe DOA with respect to an absolute position of the audio system 200within the local area. The position of the sensor array 220 may bereceived from an external system (e.g., some other component of aheadset, an artificial reality console, a mapping server, a positionsensor (e.g., the position sensor 190), etc.). The external system maycreate a virtual model of the local area, in which the local area andthe position of the audio system 200 are mapped. The received positioninformation may include a location and/or an orientation of some or allof the audio system 200 (e.g., of the sensor array 220). The DOAestimation module 240 may update the estimated DOA based on the receivedposition information.

The transfer function module 250 is configured to generate one or moreacoustic transfer functions. Generally, a transfer function is amathematical function giving a corresponding output value for eachpossible input value. Based on parameters of the detected sounds, thetransfer function module 250 generates one or more acoustic transferfunctions associated with the audio system. The acoustic transferfunctions may be array transfer functions (ATFs), head-related transferfunctions (HRTFs), other types of acoustic transfer functions, or somecombination thereof. An ATF characterizes how the microphone receives asound from a point in space.

An ATF includes a number of transfer functions that characterize arelationship between the sounds and the corresponding sound received bythe acoustic sensors in the sensor array 220. Accordingly, for a soundsource there is a corresponding transfer function for each of theacoustic sensors in the sensor array 220. And collectively the set oftransfer functions is referred to as an ATF. Note that the sound sourcemay be, e.g., someone or something generating sound in the local area,the user, or one or more transducers of the transducer array 210. TheATF for a particular sound source location relative to the sensor array220 may differ from user to user due to a person's anatomy (e.g., earshape, shoulders, etc.) that affects the sound as it travels to theperson's ears. Accordingly, the ATFs of the sensor array 220 arepersonalized for each user of the audio system 200.

In some embodiments, the transfer function module 250 determines one ormore HRTFs for a user of the audio system 200. The HRTF characterizeshow an ear receives a sound from a point in space. The HRTF for aparticular source location relative to a person is unique to each ear ofthe person (and is unique to the person) due to the person's anatomy(e.g., ear shape, shoulders, etc.) that affects the sound as it travelsto the person's ears. In some embodiments, the transfer function module250 may determine HRTFs for the user using a calibration process. Insome embodiments, the transfer function module 250 may provideinformation about the user to a remote system. The remote systemdetermines a set of HRTFs that are customized to the user using, e.g.,machine learning, and provides the customized set of HRTFs to the audiosystem 200.

The tracking module 260 is configured to track locations of one or moresound sources. The tracking module 260 may compare current DOA estimatesand compare them with a stored history of previous DOA estimates. Insome embodiments, the audio system 200 may recalculate DOA estimates ona periodic schedule, such as once per second, or once per millisecond.The tracking module may compare the current DOA estimates with previousDOA estimates, and in response to a change in a DOA estimate for a soundsource, the tracking module 260 may determine that the sound sourcemoved. In some embodiments, the tracking module 260 may detect a changein location based on visual information received from the headset orsome other external source. The tracking module 260 may track themovement of one or more sound sources over time. The tracking module 260may store values for a number of sound sources and a location of eachsound source at each point in time. In response to a change in a valueof the number or locations of the sound sources, the tracking module 260may determine that a sound source moved. The tracking module 260 maycalculate an estimate of the localization variance. The localizationvariance may be used as a confidence level for each determination of achange in movement.

The beamforming module 270 is configured to process one or more ATFs toselectively emphasize sounds from sound sources within a certain areawhile de-emphasizing sounds from other areas. In analyzing soundsdetected by the sensor array 220, the beamforming module 270 may combineinformation from different acoustic sensors to emphasize soundassociated from a particular region of the local area whiledeemphasizing sound that is from outside of the region. The beamformingmodule 270 may isolate an audio signal associated with sound from aparticular sound source from other sound sources in the local area basedon, e.g., different DOA estimates from the DOA estimation module 240 andthe tracking module 260. The beamforming module 270 may thus selectivelyanalyze discrete sound sources in the local area. In some embodiments,the beamforming module 270 may enhance a signal from a sound source. Forexample, the beamforming module 270 may apply sound filters whicheliminate signals above, below, or between certain frequencies. Signalenhancement acts to enhance sounds associated with a given identifiedsound source relative to other sounds detected by the sensor array 220.

The sound filter module 280 determines sound filters for the transducerarray 210. In some embodiments, the sound filters cause the audiocontent to be spatialized, such that the audio content appears tooriginate from a target region. The sound filter module 280 may useHRTFs and/or acoustic parameters to generate the sound filters. Theacoustic parameters describe acoustic properties of the local area. Theacoustic parameters may include, e.g., a reverberation time, areverberation level, a room impulse response, etc. In some embodiments,the sound filter module 280 calculates one or more of the acousticparameters. In some embodiments, the sound filter module 280 requeststhe acoustic parameters from a mapping server (e.g., as described belowwith regard to FIG. 5).

The sound filter module 280 provides the sound filters to the transducerarray 210. In some embodiments, the sound filters may cause positive ornegative amplification of sounds as a function of frequency.

In some embodiments, the tactility control module 285 controls thetransducer array 210 to adjust a level of tactile content imparted to auser via actuation of at least one transducer (e.g., a cartilageconduction transducer) in the transducer array 210 while presentingcontent to the user via the transducer array 210. The content caninclude audio content only, tactile content only, or combination ofaudio content and tactile content. For delivering the audio contentonly, the tactility control module 285 may adjust an actuation parameter(e.g., an input signal level) of the at least one transducer for afrequency band to be below a tactility threshold level so that a portionof the tactile content for the frequency band is not perceived by theuser. Note that values of the actuation parameter below a tactilitythreshold level correspond to ranges of actuation where a portion of thetactile content for the frequency band is not perceived by the user, andvalues at or above the tactility threshold level correspond to rangeswhere the portion of the tactile content is perceived by the user.

In one or more embodiments, the tactility control module 285 adjusts alevel of tactile content by applying a fixed actuation thresholdapproach based on, e.g., a transducer sensitivity. The transducersensitivity can be defined as a transfer function between an actuationparameter (i.e., a level of an actuating input signal, such as an inputvoltage) and an output sound pressure for a plurality of frequency bandsof sound pressure waves delivered to a user via a transducer. Foraudio-only content, the frequency bands are typical frequency bandscovering a humanly perceived acoustic spectrum, e.g., betweenapproximately 20 Hz and 20,000 Hz. For tactile-only content, thefrequency bands are limited to low frequencies, e.g., frequencies belowapproximately 500 Hz, as mechanoreceptors are primarily sensitive forfrequencies below, e.g., 500 Hz. If a sensitivity of a transducer in thetransducer array 210 is constant (e.g., over time and across multipleusers) over time and across multiple users, the tactility control module285 may derive a fixed tactility threshold level for an actuationparameter (e.g., an actuation signal) at each defined frequency band ofa plurality of frequency bands that, e.g., cover acoustic spectrumperceived by humans. The tactility control module 285 may apply, e.g., astandard dynamic range compression scheme to ensure that a level ofactuation parameter for actuation of the at least one transducer in thetransducer array 210 is below a derived tactility threshold level toavoid tactility sensation for a specific frequency band associated withthe derived tactility threshold level.

In some embodiments, the sensor array 220 detects sounds (i.e., contentincluding audio/tactile) produced by the transducer array 210 when atleast one transducer in the transducer array 210 is actuated via anactuation parameter having a set of initial values for a set offrequency bands. The tactility control module 285 may derive a tactilitythreshold level for the actuation parameter for each frequency band inthe set, based on a portion of the detected sounds within the frequencyband. The portion of the detected content within the frequency band mayinclude a certain amount of tactility content that may be larger orsmaller than a minimum level of tactile content that is sufficient to beperceived by the user for the frequency band (e.g., depending on aninitial value of the actuation parameter for the frequency band anduser's perception). The tactility control module 285 may determine thetactility threshold level for the actuation parameter for the frequencyband such that a portion of content produced by the transducer array 210for the frequency band includes approximately the minimum level oftactile content, e.g., by adjusting a level of the actuation parameterrelative to the initial value of the actuation parameter for thefrequency band. The tactility control module 285 may then adjust theactuation parameter relative to the tactility threshold level whenactuating the at least one transducer while presenting the content(i.e., audio only, tactile only, or combination of audio and tactile) tothe user. When the actuation parameter is at or above the tactilitythreshold level, a portion of tactile content for the frequency band isperceived by the user. Otherwise, if the actuation parameter is belowthe tactility threshold level, a portion of the tactile content for thefrequency band is not perceived by the user.

The tactility control module 285 may adjust a level of tactile contentby adjusting an actuation parameter of at least one transducer for afrequency band relative to a tactility threshold level by using aperception model from the data store 235. The perception model may becommon for a plurality of users and/or acoustic environments.Alternatively, each perception model in the data store 235 may be uniquefor each user and/or acoustic environment. Alternatively, a perceptionmodel may be unique for a specific group of people, e.g., one perceptionmodel may be suitable for elderly people and another perception modelmay be suitable for younger people. The tactility control module 285 maygenerate a perception model for a particular user and/or acousticenvironment by calibrating the at least one transducer in the transducerarray 210. During the calibration, the tactility control module 285determines tactility threshold levels for a plurality of frequency bandsbased on feedback responses from a user about a perceived level oftactile content for each of the frequency bands. For example, the usermay be located in a particular acoustic environment for which aperception model is generated. In one or more embodiments, instead ofrelying on user's manual feedback about the perceived tactile content,tactility sensation can be automatically detected by one or more sensorsof the sensor array 220 implemented as, e.g., non-invasive electrodesand/or implants within a tissue of the user able to sense firings ofuser's neurons.

In some embodiments, the tactility control module 285 estimates a levelof sensitivity of least one transducer in the transducer array 210 for auser, based on a portion of sounds detected by the sensor array 220within a frequency band below a defined threshold frequency. Thetactility control module 285 may then derive a tactility threshold levelfor an actuation parameter (e.g., a level of input voltage or some otheractuating signal) of at least one transducer for the frequency band,based on the estimated transducer sensitivity for the frequency band.The tactility control module 285 adjusts the actuation parameter, e.g.,to be below the tactility threshold level so that a portion of thetactile content for the frequency band is not perceived by the user.Alternatively, the tactility control module 285 adjusts the actuationparameter to be at or above the tactility threshold level so that aspecific level of the tactile content for the frequency band isperceived by the user.

This particular approach for adjusting a level of tactile content can bereferred to as an adaptive input voltage threshold approach since aninput voltage threshold is adjusted based on an estimated transducersensitivity that can vary, e.g., per user and/or over time. In one ormore embodiments when the sensitivity of the at least one transducer inthe transducer array 210 varies from one user to another, but not overtime, the tactility control module 285 may apply a one-time calibrationfor each user by utilizing, e.g., an in-ear microphone to measure atransducer sensitivity for a defined frequency band, i.e. a functionalrelation between an output sound pressure and an input voltage for eachfrequency band. Based on the measured transducer sensitivity, thetactility control module 285 may then derive a tactility threshold levelfor an actuation parameter for actuating the at least one transducer toperceive or not a portion of tactile content for a frequency band. Ifthe sensitivity of the at least one transducer in the transducer array210 varies over time as well, then the tactility control module 285 maybe configured to repeat the calibration process a specific number oftimes during a defined time period to update a tactility threshold levelfor a specific frequency band.

In one or more other embodiments, instead of the in-ear microphone,certain unique properties of cartilage conduction transducers can beleveraged to perform the calibration using microphones on a frame ofglasses, e.g., the acoustic sensors 180 mounted on the frame 110 of FIG.1A. For example, as discussed, one or more transducers in the transducerarray 210 can be implemented as cartilage conduction transducers. Thetactility sensation typically occurs in low frequency bands. If acartilage conduction transducer has a good contact with e.g., anauricular cartilage of the user's ear, the radiation pattern of acousticpressure waves in the air is mainly directional. However, if there is nodirect contact between the cartilage conduction transducer and theauricular cartilage, the radiation pattern of acoustic pressure waves inthe air may be rather omni-directional. Therefore, the tactility controlmodule 285 may be able to estimate the transducer sensitivity in the lowfrequency bands by comparing signals from microphones (e.g., theacoustic sensors 180) on both sides of the cartilage conductiontransducer of the transducer array 210.

In some embodiments, instead of the sensitivity based calibration, thetactility control module 285 may be configured to measure the inputsignal threshold curve for a range of frequencies based on a user'sfeedback on tactility sensation at a different input signal (e.g.,voltage). Instead of the user's manual feedback, a tactility sensationcan be detected by one or more sensors of the sensor array 220 that areimplemented as, e.g., non-invasive electrodes and/or implants within atissue of the user and configured to sense firings of neurons whenmechano-receptors are active. The tactility control module 285 mayderive a tactility threshold level for an actuation parameter of atleast one transducer in the transducer array 210 for the range offrequencies, based on the tactility sensations detected at the user. Thetactility control module 285 may adjust the actuation parameter for theat least one transducer to be below the threshold level so that at leasta portion of the tactile content is not perceived by the user.

In some embodiments, at least one sensor (e.g., a microphone and/oraccelerometer) of the sensor array 220 monitors a sound pressure and/oran acceleration generated by at least one transducer in the transducerarray 210 when presenting an audio signal to a user. The tactilitycontrol module 285 may then control the audio content presented to theuser based on the at least one or both of the sound pressure and theacceleration such that an amplitude of the audio content for a specificfrequency is below a threshold level. Values of the amplitude below the(tactility) threshold level correspond to the audio content where aportion of the tactile content for the frequency is not perceived by theuser, and values at or above the threshold level correspond to the audiocontent where the portion of the tactile content is perceived by theuser. Thus, in such case, the tactility control module 285 along withthe sensor array 220 performs active control of the transducer array 210for achieving tactile-free audio content. In one embodiment, a thresholdlevel for tactility sensation for a frequency (or a frequency band) canbe obtained from, e.g., a user study where an average tactilitythreshold curve is obtained for a group of subjects. In anotherembodiment, a threshold level for tactility sensation for a frequency(or a frequency band) can be obtained using an application where a usercan create its own custom tactility threshold curve, e.g., substantiallysimilar to hearing and audiometer applications.

In accordance with certain embodiments of the present disclosure, oneobjective of audio system 200 can be to augment audio experiencesthrough tactile stimulation. In the case of the audio system 200 havingthe transducer array 210 with one or more cartilage conductiontransducers at an ear's pinna for delivering audio signals, the one ormore cartilage conduction transducers may also produce tactilesensations. The tactile sensations may be a by-product of audiodelivery. Alternatively, the tactile sensations may be activelycontrolled as tactile-only signals, e.g., signals with amplitudes belowa defined threshold.

In some embodiments, the tactility control module 285 controls tactilecontent imparted to a user via actuation of at least one transducer inthe transducer array 210 to deliver navigation signals withoutdisrupting vision or interrupting other audio content, e.g., a phonecall. The controlled tactile content with navigation information can beonly content delivered to a user, or can be delivered along with audiocontent. In one or more embodiments, a tactile signal applied to atleast one cartilage conduction coupled to a corresponding ear of adriver can provide an appropriate navigation instruction. For example, abuzz on the right ear may convey the right turn instruction, a buzz onthe left ear may convey the left turn instruction, and a buzz on bothears may convey the “drive straight” instruction. The buzz may beintermittent or continuous. In one embodiment, the buzz may start faintand get stronger as the user moves closer to an intersection where theyare supposed to turn. An intermitted buzz (e.g., that faints over time)applied to a corresponding ear may convey information that the usermissed a turn. The tactility control module 285 may have informationabout the user location and moving direction from e.g., a third-partynavigation apps available on a user's mobile device. Alternatively, thetactility control module 285 may leverage the location and map from amapping server, and the mapping server may generate and providenavigation instructions to the tactility control module 285 thatappropriately controls tactile content.

In some other embodiments, the tactility control module 285 enhancesspeech intelligibility by controlling the tactile content presented to auser, e.g., along with audio content. For example, tactile stimuli canbe delivered to improve hearing of non-aspirated syllables like ‘b’ and‘p’. In such cases, the tactile stimuli can be delivered by e.g.,vibrotactile interfaces to augment hearing.

In some other embodiments, the actively controlled tactile signals canbe used for producing near-field effects. The tactility control module285 may be configured to generate audio content with a defined level ofnear field effect by controlling the tactile content. In one embodiment,the tactility control module 285 may control the tactile content toproduce the near-field effect as a more realistic percept of a virtualmosquito buzzing around an ear. In another embodiment, the tactilitycontrol module 285 may control the tactile content to produce thenear-field effect as a breath of someone whispering close to a user'sear, e.g., some other person or a virtual assistant.

Typically, audition (i.e., the act of hearing) is integrated with touchfor speech perception. For example, non-aspirated syllables like ‘b’ aremore likely heard as the aspirated ‘p’ when synchronized with air-puffson the neck or the wrist. In real-life scenario, tactile stimuli can bedelivered by vibrotactile interfaces instead of air-puffs, to augmenthearing. In noisy environments, for example, carefully delivered tactilestimuli could be used to improve speech perception. Thus, to deliver apreferred level of the tactile stimuli, the tactility control module 285may perform the natural language processing (NLP) to decode speechsignals the user is attending to. Then, the tactility control module 285may tune tactile stimuli appropriately based on the decoded speechsignals.

In some embodiments, tactile stimuli can be also delivered by devicesdesigned for audition. For example, cartilage and bone conductiontransducers in the transducer array 210 may deliver vibrations (e.g.,especially at the low-end of the frequency spectrum) that induce tactilesensations. Such parasitic signals can also be exploited to augmentspeech perception. The tactility control module 285 may control thetactile content for presentation to the user by altering spectralcontent of specific acoustic signals to increase or reduce the intensityof tactile sensations, e.g., to boost the low-end of the spectrum tomake ‘p’ more understandable and reduce it for ‘b’s. In one or moreembodiments, the tactility control module 285 performs the alteration ofspectral content based on a perception model stored in, e.g., the datastore 235 and generated based at least in part on sounds detected by thesensor array 220.

In one or more other embodiments, the tactility control module 285controls the tactile content for presentation to the user by enhancing aportion of a frequency spectrum of an audio signal. In the case of headworn AR glasses with contact transducers at the ear (e.g., the tissuetransducers 170), signals captured by a microphone array (e.g., thearray of acoustic sensors 180) can be used by the tactility controlmodule 285 to reinforce natural sound sources (e.g., another talker)with a defined combination of acoustic and tactile content.Alternatively, the tactility control module 285 may perform selectiveenhancement of a portion of the frequency spectrum through only onemodality (acoustic or tactile) to reinforce natural sound sources.

In some embodiments, the tactility control module 285 enhances a soundsource by controlling tactile content, e.g., in telepresence. Forexample, the tactility control module 285 may control the tactilecontent to make whispering perceptually more immersive and realistic(even though real whispering may not induce a tactile sensation). Thesound source enhanced by the tactility control module 285 may be locatedat a location remote from the user. The sound source may be a virtualsound source, e.g., a virtual assistant on a user's shoulder or avirtual flying insect. Alternatively, the sound sources may be abstract,such as tactile buzzing for providing directional information to theuser.

In some embodiments, the tactility control module 285 performs tactileenhancement on an audio signal to generate audio content with tactilecontent for presentation to the user. First, an acoustic signal may berecorded (e.g., by the sensor array 220) or generated (e.g., by thetactility control module 285). After that, the tactility control module285 may process the acoustic signal for tactile enhancement, byapplying, e.g., speech segmentation, frequency selective filtering,feature extraction, some other processing technique, or combinationthereof. The tactility control module 285 may then create tactilestimuli based on the processed acoustic signal. Alternatively, thetactility control module 285 may filter an audio signal to producetactile sensations when audio content is delivered to the user. Tactilesignals along with acoustic signals may be delivered via contacttransducers of the transducer array 210 located near an ear, e.g., by acartilage conduction transducer coupled to a tragus or pinna, or by abone conduction transducer.

In some embodiments, the sensor array 220 detect sounds produced by atleast one transducer (e.g., cartilage conduction transducer) in thetransducer array 210 when presenting the audio content to the user. Thetactility control module 285 may detect a level of degradation of thedetected sounds, e.g., due to cartilage conduction of acoustic pressurewaves. The tactility control module 285 may then process an audio signalto mitigate degradation of acoustic content in the audio signal, basedon the detected level of degradation. In some embodiments, the tactilitycontrol module 285 performs machine learning on the detected sounds totrain a classifier. The tactility control module 285 may apply thetrained classifier to classify the detected sounds into differentclasses (i.e., different types of degradation), based on types andfeatures of the detected sounds. The tactility control module 285 mayalso alert the user if a particular type of degradation is above athreshold level.

FIG. 2B is an example graph 290 illustrating an average tactilitythreshold level for a transducer of, e.g., the transducer array 210 inthe audio system 200 as a function of a frequency, in accordance withone or more embodiments. A curve 295 shown in FIG. 2B represents anaverage tactility threshold level (e.g., represented as a sound pressurelevel (SPL)) as a function of a frequency of tactile content. The graph290 shows threshold levels for both audibility and tactile sensation ofpresented content. Values of the SPL below the curve 295 correspond tocases when a portion of the tactile content for a specific frequency isnot perceived by an “average user.” Values of the SPL at or above thecurve 295 correspond to cases when the portion of the tactile content isperceived by the “average user.” For example, the graph 290 shows thatat 200 Hz, if the SPL created by a cartilage conduction transducer isabove approximately 80 dB, the “average user” perceives both audio andtactile simultaneously, i.e., the user not only hears but also feelssensations.

The tactility threshold curve 295 is based on tactility threshold datacollected for a group of users by averaging tactility thresholds for thegroup of users. In the illustrated embodiment, the tactility thresholddata represented by dB levels of SPL are obtained using a specific(e.g., custom-made) cartilage conduction transducer placed at a samelocation on an ear of each user. And an excitation level for thecartilage conduction transducer is incrementally increased until theperceived audio becomes bi-modal, i.e., includes audio content andtactile content. Note that different tactility threshold curves fromthat of FIG. 2B can be generated by utilizing different cartilageconduction transducers based on, e.g., amounts of energies transmittedto the skin of each user and to the air. In addition, the relationshipbetween the SPL and tactility sensations may vary when the SPL ismeasured using different transducer devices.

The tactility threshold curve 295 of FIG. 2B shows that, at lowerfrequencies, there is a higher probability of being in a tactile domainthan for higher frequencies. The tactility threshold data shown in thegraph 290 are obtained using, e.g., a microphone placed at an entranceto an ear-canal. A similar threshold curve can be obtained if anaccelerometer in contact with pinna us used. In such case, the tactilitythreshold data would represent acceleration thresholds for when thecontent can be both heard and felt. Note that the acceleration thresholdcan be converted to information about a velocity (e.g., by integration)or to information about a tissue displacement (e.g., by doubleintegration). In other embodiments (not shown in FIG. 2B), similarcurves may be obtained for bone conduction and air conduction.

FIG. 3 is a flowchart of a method 300 for adjusting a level of tactilecontent while presenting audio content, in accordance with one or moreembodiments. The process shown in FIG. 3 may be performed by componentsof an audio system (e.g., the audio system 200). Other entities mayperform some or all of the steps in FIG. 3 in other embodiments.Embodiments may include different and/or additional steps, or performthe steps in different orders. The audio system may be part of aheadset.

The audio system detects 310 (e.g., via the sensor array 220) soundsproduced by a transducer of a transducer array. The audio system maydetect a tactility sensation within a tissue of the user, e.g., via oneor more sensors coupled to the tissue or positioned in the tissue.Alternatively or additionally, the audio system may monitor a soundpressure and/or an acceleration generated by the transducer whenpresenting audio to the user. The audio system may control the audiopresented to the user based on the monitored sound pressure and/oracceleration such that an amplitude of the audio content for a definedfrequency is below a tactility threshold level. Values of the amplitudebelow the threshold level correspond to the audio where a portion of thetactile content for the frequency is not perceived by the user, andvalues at or above the threshold level correspond to the audio where theportion of the tactile content is perceived by the user.

The audio system derives 320 a tactility threshold level for anactuation parameter of the transducer for a frequency band, based on aportion of the detected sounds within the frequency band. Values of theactuation parameter below the tactility threshold level correspond toranges of actuation where a portion of the tactile content for thefrequency band is not perceived by the user and values at or above thethreshold level correspond to ranges where the portion of the tactilecontent is perceived by the user. In some embodiments, the audio systemestimates a level of sensitivity of the transducer for the user, basedon the portion of the detected sounds in a frequency band below adefined threshold frequency. The audio system derives the thresholdlevel for the actuation parameter, based on the estimated level ofsensitivity. In some other embodiments, the audio system derives thethreshold level for the actuation parameter, based on a tactilitysensation detected, e.g., by one or more sensors of the sensor array 220located within the tissue of the user.

In some embodiments, based on detected tactility sensations for aparticular user and/or acoustic environment for a plurality of frequencybands of delivered tactile content, the audio system is calibrated togenerate a perception model. The perception model may includeinformation about a tactility threshold level for an actuation parameter(e.g., input voltage) as a function of a frequency band (or frequency)for actuating the transducer. The perception model may be identical fora plurality of users and/or a plurality of acoustic environments.Alternatively, the perception model may be unique for a particular userand/or a particular acoustic environment.

The audio system adjusts 330 (e.g., via the tactility control module285) a level of tactile content to be imparted to a user via actuationof a transducer in a transducer array while presenting audio content tothe user. The audio system may adjust the level of tactile content byadjusting an actuation parameter (i.e., a level of actuation signal suchas a voltage or current) of the transducer relative to a tactilitythreshold level for a specific frequency band. In some embodiments, theaudio system adjusts the actuation parameter to be below the tactilitythreshold level when actuating the transducer so that a portion of thetactile content for the specific frequency band is not perceived by theuser. The audio system may adjust the level of tactile content based onthe perception model.

The audio system instructs 340 the transducer to present the audiocontent to the user, wherein the audio content includes the adjustedlevel of the tactile content. The audio system (e.g., the tactilitycontrol module 285) may apply a level of actuation parameter (e.g., aninput voltage level) for a frequency band to an actuator of thetransducer that is below a tactility threshold level for the frequencyband so that the user does not perceive any tactile sensation for thefrequency band.

FIG. 4 is a flowchart of a method 400 for controlling tactile contentpresented to a user, in accordance with one or more embodiments. Theprocess shown in FIG. 4 may be performed by components of an audiosystem (e.g., the audio system 200). Other entities may perform some orall of the steps in FIG. 4 in other embodiments. Embodiments may includedifferent and/or additional steps, or perform the steps in differentorders. The audio system may be part of a headset.

The audio system controls 410 (e.g., via the tactility control module285) an amount of tactile content to be imparted to a user via actuationof at least one transducer in a transducer array while presenting audiocontent to the user. The audio system may provide navigation informationby using the controlled tactile content. Furthermore, the audio systemmay increase speech intelligibility for the audio content presented tothe user by controlling the amount of the tactile content within thepresented audio content. Alternatively or additionally, the audio systemmay generate the audio content with a defined level of near field effectby controlling the amount of the tactile content within the presentedaudio content.

In some embodiments, the audio system controls the amount of the tactilecontent when generating the audio content by altering spectral contentof an input audio signal, based on a perception model (e.g., stored atthe data store 235). The audio system may detect (e.g., via a sensorarray) sounds produced by the transducer array. The audio system mayinput information about the detected sounds into the perception model toadjust a level of tactile content. In some other embodiments, the audiosystem controls the tactile content by enhancing a portion of afrequency spectrum of an audio signal when generating the audio contentfor presentation to the user. In yet some other embodiments, the audiosystem enhances a sound source by controlling the tactile content,wherein the sound source (e.g., the virtual sound source) is located ata location remotely from the user.

In some embodiments, the audio controller performs tactile enhancementon an input audio signal to create the audio content with the tactilecontent for presentation to the user. In some other embodiments, theaudio system detects (e.g., via a sensor array) sounds produced by thetransducer array that includes at least one cartilage conductiontransducer. The audio system may detect a level of degradation of thedetected sounds, e.g., due to cartilage conduction of acoustic pressurewaves. The audio system may process an audio signal to mitigatedegradation of an acoustic content in the audio content for presentationto the user, based on the detected level of degradation.

The audio system instructs 420 the transducer array to present the audiocontent to the user, wherein the audio content includes the tactilecontent. In some embodiments, the audio system provides navigationinstructions to the user using the tactile content. The transducer arraymay include a plurality of cartilage conduction transducers, wherein atleast one of the cartilage conduction transducers is attached to acorresponding ear of the user. The audio system applies the tactilecontent to the corresponding ear via the at least one cartilageconduction transducer to provide, e.g., the navigation instructions tothe user.

System Environment

FIG. 5 is a system 500 that includes a headset 505, in accordance withone or more embodiments. In some embodiments, the headset 505 may be theheadset 100 of FIG. 1A or the headset 105 of FIG. 1B. The system 500 mayoperate in an artificial reality environment (e.g., a virtual realityenvironment, an augmented reality environment, a mixed realityenvironment, or some combination thereof). The system 500 shown by FIG.5 includes the headset 505, an input/output (I/O) interface 510 that iscoupled to a console 515, a network 520, and a mapping server 525. WhileFIG. 5 shows an example system 500 including one headset 505 and one I/Ointerface 510, in other embodiments any number of these components maybe included in the system 500. For example, there may be multipleheadsets each having an associated I/O interface 510, with each headsetand I/O interface 510 communicating with the console 515. In alternativeconfigurations, different and/or additional components may be includedin the system 500. Additionally, functionality described in conjunctionwith one or more of the components shown in FIG. 5 may be distributedamong the components in a different manner than described in conjunctionwith FIG. 5 in some embodiments. For example, some or all of thefunctionality of the console 515 may be provided by the headset 505.

The headset 505 includes the display assembly 530, an optics block 535,one or more position sensors 540, and the DCA 545. Some embodiments ofheadset 505 have different components than those described inconjunction with FIG. 5. Additionally, the functionality provided byvarious components described in conjunction with FIG. 5 may bedifferently distributed among the components of the headset 505 in otherembodiments, or be captured in separate assemblies remote from theheadset 505.

The display assembly 530 displays content to the user in accordance withdata received from the console 515. The display assembly 530 displaysthe content using one or more display elements (e.g., the displayelements 120). A display element may be, e.g., an electronic display. Invarious embodiments, the display assembly 530 comprises a single displayelement or multiple display elements (e.g., a display for each eye of auser). Examples of an electronic display include: a liquid crystaldisplay (LCD), an organic light emitting diode (OLED) display, anactive-matrix organic light-emitting diode display (AMOLED), a waveguidedisplay, some other display, or some combination thereof. Note in someembodiments, the display element 120 may also include some or all of thefunctionality of the optics block 535.

The optics block 535 may magnify image light received from theelectronic display, corrects optical errors associated with the imagelight, and presents the corrected image light to one or both eyeboxes ofthe headset 505. In various embodiments, the optics block 535 includesone or more optical elements. Example optical elements included in theoptics block 535 include: an aperture, a Fresnel lens, a convex lens, aconcave lens, a filter, a reflecting surface, or any other suitableoptical element that affects image light. Moreover, the optics block 535may include combinations of different optical elements. In someembodiments, one or more of the optical elements in the optics block 535may have one or more coatings, such as partially reflective oranti-reflective coatings.

Magnification and focusing of the image light by the optics block 535allows the electronic display to be physically smaller, weigh less, andconsume less power than larger displays. Additionally, magnification mayincrease the field of view of the content presented by the electronicdisplay. For example, the field of view of the displayed content is suchthat the displayed content is presented using almost all (e.g.,approximately 110 degrees diagonal), and in some cases all, of theuser's field of view. Additionally, in some embodiments, the amount ofmagnification may be adjusted by adding or removing optical elements.

In some embodiments, the optics block 535 may be designed to correct oneor more types of optical error. Examples of optical error include barrelor pincushion distortion, longitudinal chromatic aberrations, ortransverse chromatic aberrations. Other types of optical errors mayfurther include spherical aberrations, chromatic aberrations, or errorsdue to the lens field curvature, astigmatisms, or any other type ofoptical error. In some embodiments, content provided to the electronicdisplay for display is pre-distorted, and the optics block 535 correctsthe distortion when it receives image light from the electronic displaygenerated based on the content.

The position sensor 540 is an electronic device that generates dataindicating a position of the headset 505. The position sensor 540generates one or more measurement signals in response to motion of theheadset 505. The position sensor 190 is an embodiment of the positionsensor 540. Examples of a position sensor 540 include: one or more IMUS,one or more accelerometers, one or more gyroscopes, one or moremagnetometers, another suitable type of sensor that detects motion, orsome combination thereof. The position sensor 540 may include multipleaccelerometers to measure translational motion (forward/back, up/down,left/right) and multiple gyroscopes to measure rotational motion (e.g.,pitch, yaw, roll). In some embodiments, an IMU rapidly samples themeasurement signals and calculates the estimated position of the headset505 from the sampled data. For example, the IMU integrates themeasurement signals received from the accelerometers over time toestimate a velocity vector and integrates the velocity vector over timeto determine an estimated position of a reference point on the headset505. The reference point is a point that may be used to describe theposition of the headset 505. While the reference point may generally bedefined as a point in space, however, in practice the reference point isdefined as a point within the headset 505.

The DCA 545 generates depth information for a portion of the local area.The DCA includes one or more imaging devices and a DCA controller. TheDCA 545 may also include an illuminator. Operation and structure of theDCA 545 is described above with regard to FIG. 1A.

The audio system 550 provides audio content to a user of the headset505. The audio system 550 is substantially the same as the audio system200 describe above. The audio system 550 may comprise one or acousticsensors, one or more transducers, and an audio controller. The audiosystem 550 may provide spatialized audio content to the user. In someembodiments, the audio system 550 may request acoustic parameters fromthe mapping server 525 over the network 520. The acoustic parametersdescribe one or more acoustic properties (e.g., room impulse response, areverberation time, a reverberation level, etc.) of the local area. Theaudio system 550 may also request navigation instructions from themapping server 525. For example, a user wearing the headset 505 mayprovide destination information, and the mapping server 525 may generatenavigation instructions using user location, provided destination, and amodel of area. The audio system 550 may provide information describingat least a portion of the local area from e.g., the DCA 545 and/orlocation information for the headset 505 from the position sensor 540.The audio system 550 may generate one or more sound filters using one ormore of the acoustic parameters received from the mapping server 525,and use the sound filters to provide audio content to the user.

In some embodiments, the audio system 550 controls one or moretransducers to adjust a level of tactile content imparted to the uservia actuation of the one or more transducers, e.g., while presenting theaudio content to the user. The audio system 550 may adjust the level oftactile content by adjusting an actuation parameter of the one or moretransducers for a frequency band relative to a threshold level. Valuesof the actuation parameter below the threshold level correspond toranges of actuation where a portion of the tactile content for thefrequency band is not perceived by the user, and values at or above thethreshold level correspond to ranges where the portion of the tactilecontent is perceived by the user.

In some other embodiments, the audio system 550 controls tactile contentimparted to a user via actuation of at least one transducer in atransducer array. The audio system 550 presents the controlled tactilecontent to the user, e.g., via the one or more transducers. The audiosystem 550 may provide navigation instructions to the user using thetactile content, e.g., by applying the tactile content to acorresponding ear of the user via at least one cartilage conductiontransducer attached to the ear. The audio system 550 may also increasespeech intelligibility for the audio content presented to the user bycontrolling the tactile content. Alternatively or additionally, theaudio system 550 may generate the audio content with a defined level ofnear field effect by controlling the tactile content.

The I/O interface 510 is a device that allows a user to send actionrequests and receive responses from the console 515. An action requestis a request to perform a particular action. For example, an actionrequest may be an instruction to start or end capture of image or videodata, or an instruction to perform a particular action within anapplication. The I/O interface 510 may include one or more inputdevices. Example input devices include: a keyboard, a mouse, a gamecontroller, or any other suitable device for receiving action requestsand communicating the action requests to the console 515. An actionrequest received by the I/O interface 510 is communicated to the console515, which performs an action corresponding to the action request. Insome embodiments, the I/O interface 510 includes an IMU that capturescalibration data indicating an estimated position of the I/O interface510 relative to an initial position of the I/O interface 510. In someembodiments, the I/O interface 510 may provide haptic feedback to theuser in accordance with instructions received from the console 515. Forexample, haptic feedback is provided when an action request is received,or the console 515 communicates instructions to the I/O interface 510causing the I/O interface 510 to generate haptic feedback when theconsole 515 performs an action.

The console 515 provides content to the headset 505 for processing inaccordance with information received from one or more of: the DCA 545,the headset 505, and the I/O interface 510. In the example shown in FIG.5, the console 515 includes an application store 555, a tracking module560, and an engine 565. Some embodiments of the console 515 havedifferent modules or components than those described in conjunction withFIG. 5. Similarly, the functions further described below may bedistributed among components of the console 515 in a different mannerthan described in conjunction with FIG. 5. In some embodiments, thefunctionality discussed herein with respect to the console 515 may beimplemented in the headset 505, or a remote system.

The application store 555 stores one or more applications for executionby the console 515. An application is a group of instructions, that whenexecuted by a processor, generates content for presentation to the user.Content generated by an application may be in response to inputsreceived from the user via movement of the headset 505 or the I/Ointerface 510. Examples of applications include: gaming applications,conferencing applications, video playback applications, or othersuitable applications.

The tracking module 560 tracks movements of the headset 505 or of theI/O interface 510 using information from the DCA 545, the one or moreposition sensors 540, or some combination thereof. For example, thetracking module 560 determines a position of a reference point of theheadset 505 in a mapping of a local area based on information from theheadset 505. The tracking module 560 may also determine positions of anobject or virtual object. Additionally, in some embodiments, thetracking module 560 may use portions of data indicating a position ofthe headset 505 from the position sensor 540 as well as representationsof the local area from the DCA 545 to predict a future location of theheadset 505. The tracking module 560 provides the estimated or predictedfuture position of the headset 505 or the I/O interface 510 to theengine 565.

The engine 565 executes applications and receives position information,acceleration information, velocity information, predicted futurepositions, or some combination thereof, of the headset 505 from thetracking module 560. Based on the received information, the engine 565determines content to provide to the headset 505 for presentation to theuser. For example, if the received information indicates that the userhas looked to the left, the engine 565 generates content for the headset505 that mirrors the user's movement in a virtual local area or in alocal area augmenting the local area with additional content.Additionally, the engine 565 performs an action within an applicationexecuting on the console 515 in response to an action request receivedfrom the I/O interface 510 and provides feedback to the user that theaction was performed. The provided feedback may be visual or audiblefeedback via the headset 505 or haptic feedback via the I/O interface510.

The network 520 couples the headset 505 and/or the console 515 to themapping server 525. The network 520 may include any combination of localarea and/or wide area networks using both wireless and/or wiredcommunication systems. For example, the network 520 may include theInternet, as well as mobile telephone networks. In one embodiment, thenetwork 520 uses standard communications technologies and/or protocols.Hence, the network 520 may include links using technologies such asEthernet, 802.11, worldwide interoperability for microwave access(WiMAX), 2G/3G/4G mobile communications protocols, digital subscriberline (DSL), asynchronous transfer mode (ATM), InfiniBand, PCI ExpressAdvanced Switching, etc. Similarly, the networking protocols used on thenetwork 520 can include multiprotocol label switching (MPLS), thetransmission control protocol/Internet protocol (TCP/IP), the UserDatagram Protocol (UDP), the hypertext transport protocol (HTTP), thesimple mail transfer protocol (SMTP), the file transfer protocol (FTP),etc. The data exchanged over the network 520 can be represented usingtechnologies and/or formats including image data in binary form (e.g.Portable Network Graphics (PNG)), hypertext markup language (HTML),extensible markup language (XML), etc. In addition, all or some of linkscan be encrypted using conventional encryption technologies such assecure sockets layer (SSL), transport layer security (TLS), virtualprivate networks (VPNs), Internet Protocol security (IPsec), etc.

The mapping server 525 may include a database that stores a virtualmodel describing a plurality of spaces, wherein one location in thevirtual model corresponds to a current configuration of a local area ofthe headset 505. The mapping server 525 receives, from the headset 505via the network 520, information describing at least a portion of thelocal area and/or location information for the local area. The mappingserver 525 determines, based on the received information and/or locationinformation, a location in the virtual model that is associated with thelocal area of the headset 505. The mapping server 525 determines (e.g.,retrieves) one or more acoustic parameters associated with the localarea, based in part on the determined location in the virtual model andany acoustic parameters associated with the determined location. Themapping server 525 may transmit the location of the local area and anyvalues of acoustic parameters associated with the local area to theheadset 505. The mapping server 525 may provide navigation instructionsto the audio system 550. The mapping server 525 may generate thenavigation instructions using user location, destination provided by theuser, and a model of area.

Additional Configuration Information

The foregoing description of the embodiments has been presented forillustration; it is not intended to be exhaustive or to limit the patentrights to the precise forms disclosed. Persons skilled in the relevantart can appreciate that many modifications and variations are possibleconsidering the above disclosure.

Some portions of this description describe the embodiments in terms ofalgorithms and symbolic representations of operations on information.These algorithmic descriptions and representations are commonly used bythose skilled in the data processing arts to convey the substance oftheir work effectively to others skilled in the art. These operations,while described functionally, computationally, or logically, areunderstood to be implemented by computer programs or equivalentelectrical circuits, microcode, or the like. Furthermore, it has alsoproven convenient at times, to refer to these arrangements of operationsas modules, without loss of generality. The described operations andtheir associated modules may be embodied in software, firmware,hardware, or any combinations thereof.

Any of the steps, operations, or processes described herein may beperformed or implemented with one or more hardware or software modules,alone or in combination with other devices. In one embodiment, asoftware module is implemented with a computer program productcomprising a computer-readable medium containing computer program code,which can be executed by a computer processor for performing any or allthe steps, operations, or processes described.

Embodiments may also relate to an apparatus for performing theoperations herein. This apparatus may be specially constructed for therequired purposes, and/or it may comprise a general-purpose computingdevice selectively activated or reconfigured by a computer programstored in the computer. Such a computer program may be stored in anon-transitory, tangible computer readable storage medium, or any typeof media suitable for storing electronic instructions, which may becoupled to a computer system bus. Furthermore, any computing systemsreferred to in the specification may include a single processor or maybe architectures employing multiple processor designs for increasedcomputing capability.

Embodiments may also relate to a product that is produced by a computingprocess described herein. Such a product may comprise informationresulting from a computing process, where the information is stored on anon-transitory, tangible computer readable storage medium and mayinclude any embodiment of a computer program product or other datacombination described herein.

Finally, the language used in the specification has been principallyselected for readability and instructional purposes, and it may not havebeen selected to delineate or circumscribe the patent rights. It istherefore intended that the scope of the patent rights be limited not bythis detailed description, but rather by any claims that issue on anapplication based hereon. Accordingly, the disclosure of the embodimentsis intended to be illustrative, but not limiting, of the scope of thepatent rights, which is set forth in the following claims.

What is claimed is:
 1. An audio system comprising: a transducer array configured to present audio content to a user; and a controller configured to control the transducer array to adjust a level of tactile content imparted to the user via actuation of at least one of a bone conduction transducer and a cartilage conduction transducer in the transducer array by altering a low-end of spectral content of the audio content while presenting the audio content to the user.
 2. The audio system of claim 1, wherein the controller is further configured to: adjust an actuation parameter of the at least one of the bone conduction transducer and the cartilage conduction transducer for a frequency band to be below a threshold level, wherein values of the actuation parameter below the threshold level correspond to ranges of actuation where a portion of the tactile content for the frequency band is not perceived by the user and values at or above the threshold level correspond to ranges where the portion of the tactile content is perceived by the user.
 3. The audio system of claim 2, wherein the actuation parameter of the at least one of the bone conduction transducer and the cartilage conduction transducer is a voltage applied to the at least one of the bone conduction transducer and the cartilage conduction transducer for presenting the portion of the tactile content within the frequency band to the user.
 4. The audio system of claim 1, wherein the controller is further configured to adjust the level of the tactile content using a perception model.
 5. The audio system of claim 4, wherein the perception model is unique for the user.
 6. The audio system of claim 1, wherein the controller is further configured to: generate a perception model by calibrating the transducer array; and adjust the level of the tactile content using the perception model.
 7. The audio system of claim 1, further comprising: a sensor array configured to detect sounds produced by the transducer array; and the controller is further configured to: derive a threshold level for an actuation parameter of the at least one of the bone conduction transducer and the cartilage conduction transducer for a frequency band, based on a portion of the detected sounds within the frequency band, and adjust the actuation parameter to be below the threshold level when actuating the at least one of the bone conduction transducer and the cartilage conduction transducer for presentation of a portion of the tactile content within the frequency band, values of the actuation parameter below the threshold level correspond to ranges of actuation where a portion of the tactile content for the frequency band is not perceived by the user and values at or above the threshold level correspond to ranges where the portion of the tactile content is perceived by the user.
 8. The audio system of claim 1, further comprising: a sensor array configured to detect sounds produced by the transducer array; and the controller is further configured to: estimate a level of sensitivity of the at least one of the bone conduction transducer and the cartilage conduction transducer for the user, based on a portion of the detected sounds in a frequency band below a threshold frequency, derive a threshold level for an actuation parameter of the at least one of the bone conduction transducer and the cartilage conduction transducer for the frequency band, based on the estimated level of sensitivity, and adjust the actuation parameter to be below the threshold level, wherein values of the actuation parameter below the threshold level correspond to ranges of actuation where a portion of the tactile content for the frequency band is not perceived by the user and values at or above the threshold level correspond to ranges where the portion of the tactile content is perceived by the user.
 9. The audio system of claim 1, further comprising: a sensor array configured to detect tactility sensation within a tissue of the user; and the controller is further configured to: derive a threshold level for an actuation parameter of the at least one of the bone conduction transducer and the cartilage conduction transducer for a frequency band, based on a portion of the detected tactility sensation, and adjust the actuation parameter to be below the threshold level, wherein values of the actuation parameter below the threshold level correspond to ranges of actuation where a portion of the tactile content for the frequency band is not perceived by the user and values at or above the threshold level correspond to ranges where the portion of the tactile content is perceived by the user.
 10. The audio system of claim 1, further comprising: a sensor array configured to monitor at least one of a sound pressure and an acceleration generated by the at least one of the bone conduction transducer and the cartilage conduction transducer when presenting an audio signal to the user; and the controller is further configured to control the audio content presented to the user based on the at least one of the sound pressure and the acceleration such that at least one amplitude of the audio content for at least one frequency is below a threshold level, wherein values of the at least one amplitude below the threshold level correspond to the audio content where a portion of the tactile content is not perceived by the user and values at or above the threshold level correspond to the audio content where the portion of the tactile content is perceived by the user.
 11. The audio system of claim 1, wherein the transducer array includes a plurality of cartilage conduction transducers.
 12. The audio system of claim 1, wherein the transducer array further includes at least one of: one or more air conduction transducers, a plurality of bone conduction transducers, and a plurality of cartilage conduction transducers.
 13. The audio system of claim 1, wherein the audio system is part of a headset.
 14. A method comprising: adjusting a level of tactile content to be imparted to a user via actuation of at least one of a bone conduction transducer and a cartilage conduction transducer by altering a low-end of spectral content of audio content while presenting the audio content to the user; and instructing the at least one of the bone conduction transducer and the cartilage conduction transducer to present the audio content to the user, wherein the audio content includes the adjusted level of the tactile content.
 15. The method of claim 14, further comprising: adjusting an actuation parameter of the at least one of the bone conduction transducer and the cartilage conduction transducer for a frequency band to be below a threshold level, wherein values of the actuation parameter below the threshold level correspond to ranges of actuation where a portion of the tactile content for the frequency band is not perceived by the user and values at or above the threshold level correspond to ranges where the portion of the tactile content is perceived by the user.
 16. The method of claim 14, further comprising: adjusting the level of the tactile content using a perception model.
 17. The method of claim 14, further comprising: detecting sounds produced by the at least one of the bone conduction transducer and the cartilage conduction transducer; deriving a threshold level for an actuation parameter of the at least one of the bone conduction transducer and the cartilage conduction transducer for a frequency band, based on a portion of the detected sounds within the frequency band; and adjusting the actuation parameter to be below the threshold level when actuating the at least one of the bone conduction transducer and the cartilage conduction transducer for presentation of a portion of the tactile content within the frequency band, values of the actuation parameter below the threshold level correspond to ranges of actuation where a portion of the tactile content for the frequency band is not perceived by the user and values at or above the threshold level correspond to ranges where the portion of the tactile content is perceived by the user.
 18. The method of claim 14, further comprising: detecting sounds produced by the at least one of the bone conduction transducer and the cartilage conduction transducer; estimating a level of sensitivity of the at least one of the bone conduction transducer and the cartilage conduction transducer for the user, based on a portion of the detected sounds in a frequency band below a threshold frequency; deriving a threshold level for an actuation parameter of the at least one of the bone conduction transducer and the cartilage conduction transducer for the frequency band, based on the estimated level of sensitivity; and adjusting the actuation parameter to be below the threshold level, wherein values of the actuation parameter below the threshold level correspond to ranges of actuation where a portion of the tactile content for the frequency band is not perceived by the user and values at or above the threshold level correspond to ranges where the portion of the tactile content is perceived by the user.
 19. The method of claim 14, further comprising: monitoring at least one of a sound pressure and an acceleration generated by the at least one of the bone conduction transducer and the cartilage conduction transducer when presenting an audio signal to the user; and controlling the audio content presented to the user based on the at least one of the sound pressure and the acceleration such that at least one amplitude level of the audio content for at least one frequency is below a threshold level, wherein values of the at least one amplitude below the threshold level correspond to the audio content where a portion of the tactile content is not perceived by the user and values at or above the threshold level correspond to the audio content where the portion of the tactile content is perceived by the user.
 20. A computer program product comprising a non-transitory computer-readable storage medium having instructions encoded thereon that, when executed by one or more processors, cause the one or more processors to: adjust a level of tactile content to be imparted to a user via actuation of at least one of a bone conduction transducer and a cartilage conduction transducer by altering a low-end of spectral content of audio content while presenting the audio content to the user; and instruct the at least one of the bone conduction transducer and the cartilage conduction transducer to present the audio content to the user, wherein the audio content includes the adjusted level of the tactile content. 